#include "cardboy/apps/gameboy_app.hpp"
#include "cardboy/apps/peanut_gb.h"

#include "cardboy/gfx/font16x8.hpp"
#include "cardboy/sdk/app_framework.hpp"
#include "cardboy/sdk/app_system.hpp"
#include "cardboy/sdk/services.hpp"

#include <inttypes.h>

#include <algorithm>
#include <array>
#include <cctype>
#include <cerrno>
#include <chrono>
#include <cstdint>
#include <cstdio>
#include <cstring>
#include <dirent.h>
#include <string>
#include <string_view>
#include <sys/stat.h>
#include <vector>

#define GAMEBOY_PERF_METRICS 0

#ifndef GAMEBOY_PERF_METRICS
#define GAMEBOY_PERF_METRICS 1
#endif

#if GAMEBOY_PERF_METRICS
#define GB_PERF_ONLY(...) __VA_ARGS__
#else
#define GB_PERF_ONLY(...)
#endif

namespace apps {
namespace {

constexpr int kMenuStartY  = 48;
constexpr int kMenuSpacing = font16x8::kGlyphHeight + 6;


using cardboy::sdk::AppContext;
using cardboy::sdk::AppEvent;
using cardboy::sdk::AppEventType;
using cardboy::sdk::AppTimerHandle;
using cardboy::sdk::InputState;
using cardboy::sdk::kInvalidAppTimer;
using Framebuffer = typename AppContext::Framebuffer;

constexpr std::array<std::string_view, 2> kRomExtensions = {".gb", ".gbc"};

static std::span<const EmbeddedRomDescriptor> gEmbeddedRomDescriptors{};

struct RomEntry {
    std::string    name;     // short display name
    std::string    fullPath; // absolute path on LittleFS or virtual path for embedded
    std::string    saveSlug; // base filename (without extension) used for save files
    const uint8_t* embeddedData = nullptr;
    std::size_t    embeddedSize = 0;

    [[nodiscard]] bool isEmbedded() const { return embeddedData != nullptr && embeddedSize != 0; }
};

[[nodiscard]] std::string sanitizeSaveSlug(std::string_view text) {
    std::string slug;
    slug.reserve(text.size());
    bool lastWasSeparator = false;
    for (unsigned char ch: text) {
        if (std::isalnum(ch)) {
            slug.push_back(static_cast<char>(std::tolower(ch)));
            lastWasSeparator = false;
        } else if (!slug.empty() && !lastWasSeparator) {
            slug.push_back('_');
            lastWasSeparator = true;
        }
    }
    while (!slug.empty() && slug.back() == '_')
        slug.pop_back();
    if (slug.empty())
        slug = "rom";
    return slug;
}

void appendEmbeddedRoms(std::vector<RomEntry>& out) {
    for (const auto& desc: gEmbeddedRomDescriptors) {
        if (!desc.start || !desc.end || desc.end <= desc.start)
            continue;
        const std::size_t size = static_cast<std::size_t>(desc.end - desc.start);
        if (size == 0)
            continue;
        RomEntry rom;
        rom.name = std::string(desc.name);
        const std::string slugCandidate =
                desc.saveSlug.empty() ? sanitizeSaveSlug(desc.name) : std::string(desc.saveSlug);
        rom.saveSlug     = slugCandidate.empty() ? sanitizeSaveSlug(desc.name) : slugCandidate;
        rom.fullPath     = std::string("/embedded/") + rom.saveSlug + ".gb";
        rom.embeddedData = desc.start;
        rom.embeddedSize = size;
        out.push_back(std::move(rom));
    }
}

int measureVerticalText(std::string_view text, int scale = 1, int letterSpacing = 1) {
    if (text.empty())
        return 0;
    const int advance = (font16x8::kGlyphWidth + letterSpacing) * scale;
    return static_cast<int>(text.size()) * advance - letterSpacing * scale;
}

void drawGlyphRotated(Framebuffer& fb, int x, int y, char ch, bool clockwise, int scale = 1, bool on = true) {
    const auto& rows = font16x8::glyphBitmap(ch);
    for (int row = 0; row < font16x8::kGlyphHeight; ++row) {
        const uint8_t rowBits = rows[row];
        for (int col = 0; col < font16x8::kGlyphWidth; ++col) {
            const uint8_t mask = static_cast<uint8_t>(1u << (font16x8::kGlyphWidth - 1 - col));
            if ((rowBits & mask) == 0)
                continue;
            for (int sx = 0; sx < scale; ++sx) {
                for (int sy = 0; sy < scale; ++sy) {
                    int dstX;
                    int dstY;
                    if (clockwise) {
                        dstX = x + row * scale + sx;
                        dstY = y + (font16x8::kGlyphWidth - 1 - col) * scale + sy;
                    } else {
                        dstX = x + (font16x8::kGlyphHeight - 1 - row) * scale + sx;
                        dstY = y + col * scale + sy;
                    }
                    fb.drawPixel(dstX, dstY, on);
                }
            }
        }
    }
}

void drawTextRotated(Framebuffer& fb, int x, int y, std::string_view text, bool clockwise, int scale = 1,
                     bool on = true, int letterSpacing = 1) {
    int       cursor  = y;
    const int advance = (font16x8::kGlyphWidth + letterSpacing) * scale;
    for (char ch: text) {
        drawGlyphRotated(fb, x, cursor, ch, clockwise, scale, on);
        cursor += advance;
    }
}

class GameboyApp final : public cardboy::sdk::IApp {
public:
    explicit GameboyApp(AppContext& ctx) :
        context(ctx), framebuffer(ctx.framebuffer), filesystem(ctx.filesystem()), highResClock(ctx.highResClock()) {}

    void onStart() override {
        cancelTick();
        frameDelayCarryUs = 0;
        GB_PERF_ONLY(perf.resetAll();)
        prevInput = {};
        statusMessage.clear();
        resetFpsStats();
        scaleMode     = ScaleMode::Original;
        geometryDirty = true;
        ensureFilesystemReady();
        refreshRomList();
        mode         = Mode::Browse;
        browserDirty = true;
        scheduleNextTick(0);
    }

    void onStop() override {
        cancelTick();
        frameDelayCarryUs = 0;
        GB_PERF_ONLY(perf.maybePrintAggregate(true);)
        unloadRom();
    }

    void handleEvent(const AppEvent& event) override {
        if (event.type == AppEventType::Timer && event.timer.handle == tickTimer) {
            tickTimer                   = kInvalidAppTimer;
            const uint64_t frameStartUs = nowMicros();
            performStep();
            const uint64_t frameEndUs = nowMicros();
            const uint64_t elapsedUs  = (frameEndUs >= frameStartUs) ? (frameEndUs - frameStartUs) : 0;
            GB_PERF_ONLY(printf("Step took %" PRIu64 " us\n", elapsedUs));
            scheduleAfterFrame(elapsedUs);
            return;
        }
        if (event.type == AppEventType::Button) {
            frameDelayCarryUs = 0;
            scheduleNextTick(0);
        }
    }

    void performStep() {
        GB_PERF_ONLY(perf.resetForStep();)

        GB_PERF_ONLY(const uint64_t inputStartUs = nowMicros();)
        const InputState input = context.input.readState();
        GB_PERF_ONLY(perf.inputUs = nowMicros() - inputStartUs;)

        const Mode stepMode = mode;

        switch (stepMode) {
            case Mode::Browse: {
                GB_PERF_ONLY(const uint64_t handleStartUs = nowMicros();)
                handleBrowserInput(input);
                GB_PERF_ONLY(perf.handleUs = nowMicros() - handleStartUs;)

                GB_PERF_ONLY(const uint64_t renderStartUs = nowMicros();)
                renderBrowser();
                GB_PERF_ONLY(perf.renderUs = nowMicros() - renderStartUs;)
                break;
            }
            case Mode::Running: {
                GB_PERF_ONLY(const uint64_t handleStartUs = nowMicros();)
                handleGameInput(input);
                GB_PERF_ONLY(perf.handleUs = nowMicros() - handleStartUs;)

                if (!gbReady) {
                    mode         = Mode::Browse;
                    browserDirty = true;
                    break;
                }


                GB_PERF_ONLY(const uint64_t geometryStartUs = nowMicros();)
                ensureRenderGeometry();
                GB_PERF_ONLY(perf.geometryUs = nowMicros() - geometryStartUs;)

                GB_PERF_ONLY(const uint64_t runStartUs = nowMicros();)
                gb_run_frame(&gb);
                GB_PERF_ONLY(perf.runUs = nowMicros() - runStartUs;)

                GB_PERF_ONLY(const uint64_t renderStartUs = nowMicros();)
                renderGameFrame();
                GB_PERF_ONLY(perf.renderUs = nowMicros() - renderStartUs;)
                break;
            }
        }

        prevInput = input;

        GB_PERF_ONLY(perf.finishStep();)
        GB_PERF_ONLY(perf.accumulate();)
        GB_PERF_ONLY(perf.printStep(stepMode, gbReady, frameDirty, fpsCurrent, activeRomName, roms.size(),
                                    selectedIndex, browserDirty);)
        GB_PERF_ONLY(perf.maybePrintAggregate();)
    }

private:
    enum class Mode { Browse, Running };
    enum class ScaleMode { Original, FullHeight };

    struct PerfTracker {
        enum class CallbackKind { RomRead, CartRamRead, CartRamWrite, LcdDraw, Error };

        uint64_t stepIndex     = 0;
        uint64_t stepStartUs   = 0;
        uint64_t lastStepEndUs = 0;

        uint64_t inputUs    = 0;
        uint64_t handleUs   = 0;
        uint64_t geometryUs = 0;
        uint64_t waitUs     = 0;
        uint64_t runUs      = 0;
        uint64_t renderUs   = 0;
        uint64_t totalUs    = 0;
        uint64_t otherUs    = 0;

        uint64_t cbRomReadUs      = 0;
        uint64_t cbCartReadUs     = 0;
        uint64_t cbCartWriteUs    = 0;
        uint64_t cbLcdUs          = 0;
        uint64_t cbErrorUs        = 0;
        uint32_t cbRomReadCalls   = 0;
        uint32_t cbCartReadCalls  = 0;
        uint32_t cbCartWriteCalls = 0;
        uint32_t cbLcdCalls       = 0;
        uint32_t cbErrorCalls     = 0;

        uint64_t aggStartUs          = 0;
        uint64_t aggSteps            = 0;
        uint64_t aggInputUs          = 0;
        uint64_t aggHandleUs         = 0;
        uint64_t aggGeometryUs       = 0;
        uint64_t aggWaitUs           = 0;
        uint64_t aggRunUs            = 0;
        uint64_t aggRenderUs         = 0;
        uint64_t aggTotalUs          = 0;
        uint64_t aggOtherUs          = 0;
        uint64_t aggCbRomReadUs      = 0;
        uint64_t aggCbCartReadUs     = 0;
        uint64_t aggCbCartWriteUs    = 0;
        uint64_t aggCbLcdUs          = 0;
        uint64_t aggCbErrorUs        = 0;
        uint32_t aggCbRomReadCalls   = 0;
        uint32_t aggCbCartReadCalls  = 0;
        uint32_t aggCbCartWriteCalls = 0;
        uint32_t aggCbLcdCalls       = 0;
        uint32_t aggCbErrorCalls     = 0;

        void resetAll() {
            stepIndex     = 0;
            stepStartUs   = 0;
            lastStepEndUs = 0;
            inputUs = handleUs = geometryUs = waitUs = runUs = renderUs = totalUs = otherUs = 0;
            cbRomReadUs = cbCartReadUs = cbCartWriteUs = cbLcdUs = cbErrorUs = 0;
            cbRomReadCalls = cbCartReadCalls = cbCartWriteCalls = cbLcdCalls = cbErrorCalls = 0;
            resetAggregate(0);
        }

        void resetForStep() {
            stepStartUs = clockMicros();
            inputUs = handleUs = geometryUs = waitUs = runUs = renderUs = totalUs = otherUs = 0;
            cbRomReadUs = cbCartReadUs = cbCartWriteUs = cbLcdUs = cbErrorUs = 0;
            cbRomReadCalls = cbCartReadCalls = cbCartWriteCalls = cbLcdCalls = cbErrorCalls = 0;
        }

        void finishStep() {
            const uint64_t now       = clockMicros();
            totalUs                  = now - stepStartUs;
            lastStepEndUs            = now;
            const uint64_t accounted = inputUs + handleUs + geometryUs + waitUs + runUs + renderUs;
            otherUs                  = (totalUs >= accounted) ? (totalUs - accounted) : 0;
        }

        void addCallback(CallbackKind kind, uint64_t durationUs) {
            switch (kind) {
                case CallbackKind::RomRead:
                    cbRomReadUs += durationUs;
                    ++cbRomReadCalls;
                    break;
                case CallbackKind::CartRamRead:
                    cbCartReadUs += durationUs;
                    ++cbCartReadCalls;
                    break;
                case CallbackKind::CartRamWrite:
                    cbCartWriteUs += durationUs;
                    ++cbCartWriteCalls;
                    break;
                case CallbackKind::LcdDraw:
                    cbLcdUs += durationUs;
                    ++cbLcdCalls;
                    break;
                case CallbackKind::Error:
                    cbErrorUs += durationUs;
                    ++cbErrorCalls;
                    break;
            }
        }

        void accumulate() {
            ++stepIndex;
            if (!aggStartUs)
                aggStartUs = stepStartUs;
            ++aggSteps;
            aggInputUs += inputUs;
            aggHandleUs += handleUs;
            aggGeometryUs += geometryUs;
            aggWaitUs += waitUs;
            aggRunUs += runUs;
            aggRenderUs += renderUs;
            aggTotalUs += totalUs;
            aggOtherUs += otherUs;
            aggCbRomReadUs += cbRomReadUs;
            aggCbCartReadUs += cbCartReadUs;
            aggCbCartWriteUs += cbCartWriteUs;
            aggCbLcdUs += cbLcdUs;
            aggCbErrorUs += cbErrorUs;
            aggCbRomReadCalls += cbRomReadCalls;
            aggCbCartReadCalls += cbCartReadCalls;
            aggCbCartWriteCalls += cbCartWriteCalls;
            aggCbLcdCalls += cbLcdCalls;
            aggCbErrorCalls += cbErrorCalls;
        }

        void printStep(Mode stepMode, bool gbReady, bool frameDirty, uint32_t fps, const std::string& romName,
                       std::size_t romCount, std::size_t selectedIdx, bool browserDirty) const {
            auto              toMs    = [](uint64_t us) { return static_cast<double>(us) / 1000.0; };
            const char*       modeStr = (stepMode == Mode::Running) ? "RUN" : "BROWSE";
            const char*       name    = romName.empty() ? "-" : romName.c_str();
            const std::size_t safeIdx = (romCount == 0) ? 0 : std::min(selectedIdx, romCount - 1);
            std::printf(
                    "GB STEP #%llu [%s] total=%.3fms input=%.3fms handle=%.3fms geom=%.3fms wait=%.3fms run=%.3fms "
                    "render=%.3fms other=%.3fms | cb lcd=%.3fms/%lu rom=%.3fms/%lu cramR=%.3fms/%lu cramW=%.3fms/%lu "
                    "err=%.3fms/%lu | info gbReady=%d frameDirty=%d fps=%lu rom='%s' roms=%zu sel=%zu dirty=%d\n",
                    static_cast<unsigned long long>(stepIndex), modeStr, toMs(totalUs), toMs(inputUs), toMs(handleUs),
                    toMs(geometryUs), toMs(waitUs), toMs(runUs), toMs(renderUs), toMs(otherUs), toMs(cbLcdUs),
                    static_cast<unsigned long>(cbLcdCalls), toMs(cbRomReadUs),
                    static_cast<unsigned long>(cbRomReadCalls), toMs(cbCartReadUs),
                    static_cast<unsigned long>(cbCartReadCalls), toMs(cbCartWriteUs),
                    static_cast<unsigned long>(cbCartWriteCalls), toMs(cbErrorUs),
                    static_cast<unsigned long>(cbErrorCalls), gbReady ? 1 : 0, frameDirty ? 1 : 0,
                    static_cast<unsigned long>(fps), name, romCount, safeIdx, browserDirty ? 1 : 0);
        }

        void maybePrintAggregate(bool force = false) {
            if (!aggSteps)
                return;
            if (!aggStartUs)
                aggStartUs = stepStartUs;
            const uint64_t now  = lastStepEndUs ? lastStepEndUs : clockMicros();
            const uint64_t span = now - aggStartUs;
            if (!force && span < 1000000ULL)
                return;
            const double spanSec   = span ? static_cast<double>(span) / 1e6 : 0.0;
            auto         avgStepMs = [&](uint64_t total) {
                return aggSteps ? static_cast<double>(total) / static_cast<double>(aggSteps) / 1000.0 : 0.0;
            };
            auto avgCallMs = [&](uint64_t total, uint32_t calls) {
                return calls ? static_cast<double>(total) / static_cast<double>(calls) / 1000.0 : 0.0;
            };
            std::printf("GB PERF %llu steps span=%.3fs%s | avg total=%.3fms input=%.3fms handle=%.3fms geom=%.3fms "
                        "wait=%.3fms "
                        "run=%.3fms render=%.3fms other=%.3fms | cb avg lcd=%.3fms (%lu) rom=%.3fms (%lu) cramR=%.3fms "
                        "(%lu) "
                        "cramW=%.3fms (%lu) err=%.3fms (%lu)\n",
                        static_cast<unsigned long long>(aggSteps), spanSec, force ? " (flush)" : "",
                        avgStepMs(aggTotalUs), avgStepMs(aggInputUs), avgStepMs(aggHandleUs), avgStepMs(aggGeometryUs),
                        avgStepMs(aggWaitUs), avgStepMs(aggRunUs), avgStepMs(aggRenderUs), avgStepMs(aggOtherUs),
                        avgCallMs(aggCbLcdUs, aggCbLcdCalls), static_cast<unsigned long>(aggCbLcdCalls),
                        avgCallMs(aggCbRomReadUs, aggCbRomReadCalls), static_cast<unsigned long>(aggCbRomReadCalls),
                        avgCallMs(aggCbCartReadUs, aggCbCartReadCalls), static_cast<unsigned long>(aggCbCartReadCalls),
                        avgCallMs(aggCbCartWriteUs, aggCbCartWriteCalls),
                        static_cast<unsigned long>(aggCbCartWriteCalls), avgCallMs(aggCbErrorUs, aggCbErrorCalls),
                        static_cast<unsigned long>(aggCbErrorCalls));
            resetAggregate(now);
        }

    private:
        void resetAggregate(uint64_t newStart) {
            aggStartUs          = newStart;
            aggSteps            = 0;
            aggInputUs          = 0;
            aggHandleUs         = 0;
            aggGeometryUs       = 0;
            aggWaitUs           = 0;
            aggRunUs            = 0;
            aggRenderUs         = 0;
            aggTotalUs          = 0;
            aggOtherUs          = 0;
            aggCbRomReadUs      = 0;
            aggCbCartReadUs     = 0;
            aggCbCartWriteUs    = 0;
            aggCbLcdUs          = 0;
            aggCbErrorUs        = 0;
            aggCbRomReadCalls   = 0;
            aggCbCartReadCalls  = 0;
            aggCbCartWriteCalls = 0;
            aggCbLcdCalls       = 0;
            aggCbErrorCalls     = 0;
        }

        static uint64_t clockMicros() {
            const auto now = std::chrono::steady_clock::now();
            return static_cast<uint64_t>(
                    std::chrono::duration_cast<std::chrono::microseconds>(now.time_since_epoch()).count());
        }
    };

    class ScopedCallbackTimer {
    public:
        ScopedCallbackTimer(GameboyApp* instance, PerfTracker::CallbackKind kind) {
#if GAMEBOY_PERF_METRICS
            if (instance) {
                app     = instance;
                cbKind  = kind;
                startUs = instance->nowMicros();
            }
#else
            (void) instance;
            (void) kind;
#endif
        }

        ~ScopedCallbackTimer() {
#if GAMEBOY_PERF_METRICS
            if (!app)
                return;
            const uint64_t end = app->nowMicros();
            app->perf.addCallback(cbKind, end - startUs);
#endif
        }

    private:
#if GAMEBOY_PERF_METRICS
        GameboyApp*               app = nullptr;
        PerfTracker::CallbackKind cbKind{};
        uint64_t                  startUs = 0;
#endif
    };

    struct RenderGeometry {
        float                       scaleX       = 1.0f;
        float                       scaleY       = 1.0f;
        int                         scaledWidth  = LCD_WIDTH;
        int                         scaledHeight = LCD_HEIGHT;
        int                         offsetX      = 0;
        int                         offsetY      = 0;
        int                         leftMargin   = 0;
        int                         rightMargin  = 0;
        std::array<int, LCD_HEIGHT> lineYStart{};
        std::array<int, LCD_HEIGHT> lineYEnd{};
        std::array<int, LCD_WIDTH>  colXStart{};
        std::array<int, LCD_WIDTH>  colXEnd{};
    };

    AppContext&                  context;
    Framebuffer&                 framebuffer;
    cardboy::sdk::IFilesystem*   filesystem   = nullptr;
    cardboy::sdk::IHighResClock* highResClock = nullptr;
    PerfTracker                  perf{};
    AppTimerHandle               tickTimer         = kInvalidAppTimer;
    int64_t                      frameDelayCarryUs = 0;
    static constexpr uint32_t    kTargetFrameUs    = 1000000 / 60; // ~16.6 ms

    Mode                  mode          = Mode::Browse;
    ScaleMode             scaleMode     = ScaleMode::Original;
    bool                  geometryDirty = true;
    RenderGeometry        geometry{};
    std::vector<RomEntry> roms;
    std::size_t           selectedIndex = 0;
    bool                  browserDirty  = true;
    std::string           statusMessage;
    InputState            prevInput{};

    // Emulator state
    struct gb_s          gb{};
    bool                 gbReady = false;
    std::vector<uint8_t> romData;
    const uint8_t*       romDataView     = nullptr;
    std::size_t          romDataViewSize = 0;
    std::vector<uint8_t> cartRam;
    bool                 frameDirty        = false;
    uint32_t             fpsLastSampleMs   = 0;
    uint32_t             fpsFrameCounter   = 0;
    uint32_t             totalFrameCounter = 0;
    uint32_t             fpsCurrent        = 0;
    std::string          activeRomName;
    std::string          activeRomSavePath;

    void cancelTick() {
        if (tickTimer != kInvalidAppTimer) {
            context.cancelTimer(tickTimer);
            tickTimer = kInvalidAppTimer;
        }
    }

    void scheduleNextTick(uint32_t delayMs) {
        cancelTick();
        tickTimer = context.scheduleTimer(delayMs, false);
    }

    uint32_t idleDelayMs() const { return browserDirty ? 50 : 140; }

    void scheduleAfterFrame(uint64_t elapsedUs) {
        if (mode == Mode::Running && gbReady) {
            int64_t desiredUs = static_cast<int64_t>(kTargetFrameUs) - static_cast<int64_t>(elapsedUs);
            desiredUs += frameDelayCarryUs;
            if (desiredUs <= 0) {
                frameDelayCarryUs = desiredUs;
                scheduleNextTick(0);
                return;
            }
            frameDelayCarryUs = desiredUs % 1000;
            desiredUs -= frameDelayCarryUs;
            uint32_t delayMs = static_cast<uint32_t>(desiredUs / 1000);
            scheduleNextTick(delayMs);
            return;
        }
        frameDelayCarryUs = 0;
        scheduleNextTick(idleDelayMs());
    }

    bool ensureFilesystemReady() {
        if (!filesystem) {
            setStatus("Storage unavailable");
            return false;
        }

        if (!filesystem->isMounted() && !filesystem->mount()) {
            setStatus("Storage mount failed");
            return false;
        }

        const std::string romDir = romDirectory();
        struct stat       st{};
        if (stat(romDir.c_str(), &st) == 0) {
            if (S_ISDIR(st.st_mode))
                return true;
            setStatus("ROM path not dir");
            return false;
        }

        if (mkdir(romDir.c_str(), 0775) == 0)
            return true;

        if (errno == EEXIST)
            return true;

        setStatus("ROM dir mkdir failed");
        return false;
    }

    [[nodiscard]] std::string romDirectory() const {
        std::string result;
        if (filesystem)
            result = filesystem->basePath();
        if (!result.empty() && result.back() != '/')
            result.push_back('/');
        result.append("roms");
        return result;
    }

    static bool hasRomExtension(std::string_view name) {
        const auto dotPos = name.find_last_of('.');
        if (dotPos == std::string_view::npos)
            return false;
        std::string ext(name.substr(dotPos));
        std::transform(ext.begin(), ext.end(), ext.begin(),
                       [](unsigned char ch) { return static_cast<char>(std::tolower(ch)); });
        return std::any_of(kRomExtensions.begin(), kRomExtensions.end(),
                           [&](std::string_view allowed) { return ext == allowed; });
    }

    void refreshRomList() {
        roms.clear();

        bool        fsMounted = filesystem ? filesystem->isMounted() : false;
        std::string statusHint;
        const auto  updateStatusHintIfEmpty = [&](std::string value) {
            if (statusHint.empty())
                statusHint = std::move(value);
        };

        if (!fsMounted) {
            fsMounted = ensureFilesystemReady();
            if (!fsMounted)
                updateStatusHintIfEmpty("Built-in ROMs only (filesystem unavailable)");
        }

        if (fsMounted) {
            const std::string dirPath = romDirectory();
            if (DIR* dir = opendir(dirPath.c_str())) {
                while (dirent* entry = readdir(dir)) {
                    const std::string_view name(entry->d_name);
                    if (name == "." || name == "..")
                        continue;
                    if (!hasRomExtension(name))
                        continue;
                    RomEntry rom;
                    rom.fullPath = dirPath;
                    if (!rom.fullPath.empty() && rom.fullPath.back() != '/')
                        rom.fullPath.push_back('/');
                    rom.fullPath.append(entry->d_name);

                    std::string displayName(entry->d_name);
                    const auto  dotPos = displayName.find_last_of('.');
                    if (dotPos != std::string::npos)
                        displayName.resize(dotPos);
                    rom.name = displayName;

                    std::string slugCandidate(entry->d_name);
                    if (dotPos != std::string::npos)
                        slugCandidate.resize(dotPos);
                    if (slugCandidate.empty())
                        slugCandidate = sanitizeSaveSlug(displayName);
                    rom.saveSlug = slugCandidate.empty() ? sanitizeSaveSlug(displayName) : slugCandidate;

                    roms.push_back(std::move(rom));
                }
                closedir(dir);
                if (roms.empty())
                    updateStatusHintIfEmpty("Copy .gb/.gbc into ROMS/");
            } else {
                updateStatusHintIfEmpty("ROM directory missing");
            }
        }

        appendEmbeddedRoms(roms);

        std::sort(roms.begin(), roms.end(), [](const RomEntry& a, const RomEntry& b) { return a.name < b.name; });

        if (selectedIndex >= roms.size())
            selectedIndex = roms.empty() ? 0 : roms.size() - 1;

        browserDirty = true;

        if (roms.empty()) {
            setStatus("No ROMs available");
        } else if (!statusHint.empty()) {
            setStatus(statusHint);
        } else {
            statusMessage.clear();
        }
    }

    void toggleScaleMode() {
        if (scaleMode == ScaleMode::Original)
            scaleMode = ScaleMode::FullHeight;
        else
            scaleMode = ScaleMode::Original;
        geometryDirty = true;
        frameDirty    = true;
        setStatus(scaleMode == ScaleMode::FullHeight ? "Scale: Full height" : "Scale: Original");
    }

    void ensureRenderGeometry() {
        if (!geometryDirty)
            return;
        geometryDirty = false;

        auto&      geom      = geometry;
        const int  fbWidth   = framebuffer.width();
        const int  fbHeight  = framebuffer.height();
        const auto resetGeom = [&]() {
            geom.scaleX       = 1.0f;
            geom.scaleY       = 1.0f;
            geom.scaledWidth  = 0;
            geom.scaledHeight = 0;
            geom.offsetX      = 0;
            geom.offsetY      = 0;
            geom.leftMargin   = 0;
            geom.rightMargin  = 0;
            std::fill(geom.lineYStart.begin(), geom.lineYStart.end(), 0);
            std::fill(geom.lineYEnd.begin(), geom.lineYEnd.end(), 0);
            std::fill(geom.colXStart.begin(), geom.colXStart.end(), 0);
            std::fill(geom.colXEnd.begin(), geom.colXEnd.end(), 0);
        };

        if (fbWidth <= 0 || fbHeight <= 0) {
            resetGeom();
            return;
        }

        int scaledWidth;
        int scaledHeight;
        if (scaleMode == ScaleMode::FullHeight) {
            int targetHeight = fbHeight;
            int targetWidth  = static_cast<int>((static_cast<int64_t>(LCD_WIDTH) * targetHeight + LCD_HEIGHT / 2) /
                                                std::max(1, LCD_HEIGHT));
            if (targetWidth > fbWidth) {
                targetWidth  = fbWidth;
                targetHeight = static_cast<int>((static_cast<int64_t>(LCD_HEIGHT) * targetWidth + LCD_WIDTH / 2) /
                                                std::max(1, LCD_WIDTH));
            }
            scaledWidth  = std::clamp(targetWidth, 1, fbWidth);
            scaledHeight = std::clamp(targetHeight, 1, fbHeight);
        } else {
            scaledWidth  = std::clamp(fbWidth, 1, LCD_WIDTH);
            scaledHeight = std::clamp(fbHeight, 1, LCD_HEIGHT);
        }

        geom.scaledWidth  = scaledWidth;
        geom.scaledHeight = scaledHeight;
        geom.offsetX      = std::max(0, (fbWidth - scaledWidth) / 2);
        geom.offsetY      = std::max(0, (fbHeight - scaledHeight) / 2);
        geom.leftMargin   = geom.offsetX;
        geom.rightMargin  = std::max(0, fbWidth - (geom.offsetX + scaledWidth));
        geom.scaleX       = static_cast<float>(scaledWidth) / static_cast<float>(LCD_WIDTH);
        geom.scaleY       = static_cast<float>(scaledHeight) / static_cast<float>(LCD_HEIGHT);

        for (int srcLine = 0; srcLine < LCD_HEIGHT; ++srcLine) {
            int start = geom.offsetY + static_cast<int>((static_cast<int64_t>(scaledHeight) * srcLine) / LCD_HEIGHT);
            int end =
                    geom.offsetY + static_cast<int>((static_cast<int64_t>(scaledHeight) * (srcLine + 1)) / LCD_HEIGHT);
            start                    = std::clamp(start, 0, fbHeight);
            end                      = std::clamp(end, start, fbHeight);
            geom.lineYStart[srcLine] = start;
            geom.lineYEnd[srcLine]   = end;
        }

        for (int srcCol = 0; srcCol < LCD_WIDTH; ++srcCol) {
            int start = geom.offsetX + static_cast<int>((static_cast<int64_t>(scaledWidth) * srcCol) / LCD_WIDTH);
            int end   = geom.offsetX + static_cast<int>((static_cast<int64_t>(scaledWidth) * (srcCol + 1)) / LCD_WIDTH);
            start     = std::clamp(start, 0, fbWidth);
            end       = std::clamp(end, start, fbWidth);
            geom.colXStart[srcCol] = start;
            geom.colXEnd[srcCol]   = end;
        }
    }

    void handleBrowserInput(const InputState& input) {
        if (input.select && !prevInput.select) {
            refreshRomList();
            browserDirty = true;
            if (roms.empty())
                return;
        }

        if (roms.empty())
            return;
        const auto wrapDecrement = [&]() {
            if (selectedIndex == 0)
                selectedIndex = roms.size() - 1;
            else
                --selectedIndex;
            browserDirty = true;
        };

        const auto wrapIncrement = [&]() {
            selectedIndex = (selectedIndex + 1) % roms.size();
            browserDirty  = true;
        };

        if (input.up && !prevInput.up)
            wrapDecrement();
        else if (input.down && !prevInput.down)
            wrapIncrement();

        const bool launchRequested = (input.a && !prevInput.a) || (input.start && !prevInput.start);
        if (launchRequested)
            loadRom(selectedIndex);
    }

    void renderBrowser() {
        if (!browserDirty)
            return;
        browserDirty = false;

        framebuffer.frameReady();

        const std::string_view title      = "GAME BOY";
        const int              titleWidth = font16x8::measureText(title, 2, 1);
        const int              titleX     = (framebuffer.width() - titleWidth) / 2;
        font16x8::drawText(framebuffer, titleX, 12, title, 2, true, 1);

        if (roms.empty()) {
            font16x8::drawText(framebuffer, 24, kMenuStartY + 12, "NO ROMS FOUND", 1, true, 1);
            font16x8::drawText(framebuffer, 24, kMenuStartY + kMenuSpacing + 12, "ADD FILES TO ROMS/", 1, true, 1);
        } else {
            const std::size_t visibleCount =
                    static_cast<std::size_t>(std::max(1, (framebuffer.height() - kMenuStartY - 64) / kMenuSpacing));
            std::size_t first = 0;
            if (roms.size() > visibleCount) {
                if (selectedIndex >= visibleCount / 2)
                    first = selectedIndex - visibleCount / 2;
                if (first + visibleCount > roms.size())
                    first = roms.size() - visibleCount;
            }

            for (std::size_t i = 0; i < visibleCount && (first + i) < roms.size(); ++i) {
                const std::size_t idx       = first + i;
                const bool        selected  = (idx == selectedIndex);
                const int         y         = kMenuStartY + static_cast<int>(i) * kMenuSpacing;
                std::string       labelText = roms[idx].name.empty() ? "(unnamed)" : roms[idx].name;
                if (roms[idx].isEmbedded())
                    labelText.append(" *");
                if (selected)
                    font16x8::drawText(framebuffer, 16, y, ">", 1, true, 1);
                font16x8::drawText(framebuffer, selected ? 32 : 40, y, labelText, 1, true, 1);
            }

            font16x8::drawText(framebuffer, 16, framebuffer.height() - 52, "A/START PLAY", 1, true, 1);
            font16x8::drawText(framebuffer, 16, framebuffer.height() - 32, "SELECT RESCAN", 1, true, 1);
        }

        if (!statusMessage.empty()) {
            const int textWidth = font16x8::measureText(statusMessage, 1, 1);
            const int x         = std::max(12, (framebuffer.width() - textWidth) / 2);
            font16x8::drawText(framebuffer, x, framebuffer.height() - 16, statusMessage, 1, true, 1);
        }

        framebuffer.sendFrame();
    }

    bool loadRom(std::size_t index) {
        if (index >= roms.size())
            return false;

        unloadRom();

        const RomEntry& rom = roms[index];
        romDataView         = nullptr;
        romDataViewSize     = 0;
        if (rom.isEmbedded()) {
            if (rom.embeddedSize == 0) {
                setStatus("ROM empty");
                return false;
            }
            romData.clear();
            romDataView     = rom.embeddedData;
            romDataViewSize = rom.embeddedSize;
        } else {
            FILE* file = std::fopen(rom.fullPath.c_str(), "rb");
            if (!file) {
                setStatus("Open ROM failed");
                return false;
            }

            if (std::fseek(file, 0, SEEK_END) != 0) {
                setStatus("ROM seek failed");
                std::fclose(file);
                return false;
            }
            const long size = std::ftell(file);
            if (size <= 0) {
                setStatus("ROM empty");
                std::fclose(file);
                return false;
            }
            std::rewind(file);

            romData.resize(static_cast<std::size_t>(size));
            const size_t readBytes = std::fread(romData.data(), 1, romData.size(), file);
            std::fclose(file);
            if (readBytes != romData.size()) {
                setStatus("ROM read failed");
                romData.clear();
                return false;
            }
            romDataView     = romData.data();
            romDataViewSize = romData.size();
        }

        if (!romDataView || romDataViewSize == 0) {
            setStatus("ROM load failed");
            romData.clear();
            romDataView     = nullptr;
            romDataViewSize = 0;
            return false;
        }

        std::memset(&gb, 0, sizeof(gb));
        const auto initResult = gb_init(&gb, &GameboyApp::romRead, &GameboyApp::cartRamRead, &GameboyApp::cartRamWrite,
                                        &GameboyApp::errorCallback, this);
        if (initResult != GB_INIT_NO_ERROR) {
            setStatus(initErrorToString(initResult));
            romData.clear();
            romDataView     = nullptr;
            romDataViewSize = 0;
            return false;
        }

        gb.direct.priv   = this;
        gb.direct.joypad = 0xFF;

        gb_init_lcd(&gb, &GameboyApp::lcdDrawLine);

        gb.direct.interlace  = false;
        gb.direct.frame_skip = true;

        const uint_fast32_t saveSize = gb_get_save_size(&gb);
        cartRam.assign(static_cast<std::size_t>(saveSize), 0);
        std::string savePath;
        const bool  fsReady = (filesystem && filesystem->isMounted()) || ensureFilesystemReady();
        if (fsReady)
            savePath = buildSavePath(rom, romDirectory());
        activeRomSavePath = savePath;
        loadSaveFile();

        resetFpsStats();
        fpsLastSampleMs = context.clock.millis();

        gbReady       = true;
        mode          = Mode::Running;
        frameDirty    = true;
        geometryDirty = true;
        activeRomName = rom.name.empty() ? "Game" : rom.name;

        std::string statusText = "Running " + activeRomName;
        if (!fsReady)
            statusText.append(" (no save)");
        setStatus(std::move(statusText));
        return true;
    }

    void unloadRom() {
        if (!gbReady) {
            resetFpsStats();
            romData.clear();
            romDataView     = nullptr;
            romDataViewSize = 0;
            cartRam.clear();
            activeRomName.clear();
            activeRomSavePath.clear();
            geometryDirty = true;
            return;
        }

        maybeSaveRam();
        resetFpsStats();

        gbReady = false;
        romData.clear();
        romDataView     = nullptr;
        romDataViewSize = 0;
        cartRam.clear();
        activeRomName.clear();
        activeRomSavePath.clear();
        geometryDirty = true;
        std::memset(&gb, 0, sizeof(gb));
        mode         = Mode::Browse;
        browserDirty = true;
    }

    void handleGameInput(const InputState& input) {
        if (!gbReady)
            return;

        const bool scaleToggleCombo = input.start && input.b && !(prevInput.start && prevInput.b);
        if (scaleToggleCombo)
            toggleScaleMode();

        uint8_t joypad = 0xFF;
        if (input.a)
            joypad &= ~JOYPAD_A;
        if (input.b)
            joypad &= ~JOYPAD_B;
        if (input.select)
            joypad &= ~JOYPAD_SELECT;
        if (input.start)
            joypad &= ~JOYPAD_START;
        if (input.up)
            joypad &= ~JOYPAD_UP;
        if (input.down)
            joypad &= ~JOYPAD_DOWN;
        if (input.left)
            joypad &= ~JOYPAD_LEFT;
        if (input.right)
            joypad &= ~JOYPAD_RIGHT;

        gb.direct.joypad = joypad;

        const bool exitComboPressed     = input.start && input.select;
        const bool exitComboJustPressed = exitComboPressed && !(prevInput.start && prevInput.select);
        if (exitComboJustPressed) {
            setStatus("Saved " + activeRomName);
            unloadRom();
        }
    }

    void renderGameFrame() {
        if (!frameDirty)
            return;
        frameDirty = false;

        ensureRenderGeometry();

        ++fpsFrameCounter;
        ++totalFrameCounter;
        const uint32_t nowMs = context.clock.millis();
        if (fpsLastSampleMs == 0)
            fpsLastSampleMs = nowMs;
        const uint32_t elapsed = nowMs - fpsLastSampleMs;
        if (elapsed >= 1000U) {
            const uint64_t scaledFrames = static_cast<uint64_t>(fpsFrameCounter) * 1000ULL;
            fpsCurrent                  = static_cast<uint32_t>(scaledFrames / elapsed);
            fpsFrameCounter             = 0;
            fpsLastSampleMs             = nowMs;
        }

        char fpsValueBuf[16];
        std::snprintf(fpsValueBuf, sizeof(fpsValueBuf), "%u", static_cast<unsigned>(fpsCurrent));
        const std::string fpsValue(fpsValueBuf);
        const std::string fpsLabel  = "FPS";
        const std::string fpsText   = fpsValue + " FPS";
        const std::string scaleHint = (scaleMode == ScaleMode::FullHeight) ? "START+B NORMAL" : "START+B SCALE";

        if (scaleMode == ScaleMode::FullHeight) {
            const auto& geom          = geometry;
            const int   textScale     = 1;
            const int   rotatedWidth  = font16x8::kGlyphHeight * textScale;
            const int   screenHeight  = framebuffer.height();
            const int   screenWidth   = framebuffer.width();
            const int   leftMargin    = std::max(0, geom.leftMargin);
            const int   rightMargin   = std::max(0, geom.rightMargin);
            const int   maxLeftX      = std::max(0, screenWidth - rotatedWidth);
            const int   maxRightXBase = std::max(0, screenWidth - rotatedWidth);


            const int horizontalPadding = 8;
            const int fpsLineGap        = 4;
            const int fpsLabelWidth     = font16x8::measureText(fpsLabel, 1, 1);
            const int fpsValueWidth     = font16x8::measureText(fpsValue, 1, 1);
            const int fpsBlockWidth     = std::max(fpsLabelWidth, fpsValueWidth);
            int       fpsX              = std::max(0, screenWidth - fpsBlockWidth - horizontalPadding);
            const int fpsY              = horizontalPadding;
            font16x8::drawText(framebuffer, fpsX, fpsY, fpsLabel, 1, true, 1);
            font16x8::drawText(framebuffer, fpsX, fpsY + font16x8::kGlyphHeight + fpsLineGap, fpsValue, 1, true, 1);
            const int reservedTop = fpsY + (font16x8::kGlyphHeight * 2) + fpsLineGap + horizontalPadding;

            if (!activeRomName.empty()) {
                const std::string rotatedRomName(activeRomName.rbegin(), activeRomName.rend());
                const int         textHeight = measureVerticalText(rotatedRomName, textScale);
                const int         maxOrigin  = std::max(0, screenHeight - textHeight);
                int               leftX      = 8;
                int               leftY      = std::clamp((screenHeight - textHeight) / 2, 0, maxOrigin);
                drawTextRotated(framebuffer, leftX, leftY, rotatedRomName, true, textScale, true, 1);
                if (!statusMessage.empty()) {
                    const std::string rotatedStatusMessage(statusMessage.rbegin(), statusMessage.rend());
                    const int         textHeight = measureVerticalText(rotatedStatusMessage, textScale);
                    const int         maxOrigin  = std::max(0, screenHeight - textHeight);
                    leftX                        = leftX + 20;
                    leftY                        = std::clamp((screenHeight - textHeight) / 2, 0, maxOrigin);
                    drawTextRotated(framebuffer, leftX, leftY, rotatedStatusMessage, true, textScale, true, 1);
                }
            }


            std::vector<std::string_view> rightTexts;
            rightTexts.reserve(2U);
            rightTexts.emplace_back("START+SELECT BACK");
            rightTexts.emplace_back(scaleHint);

            const int gap              = 8;
            int       totalRightHeight = 0;
            for (std::string_view text: rightTexts) {
                if (text.empty())
                    continue;
                std::string rotated(text.rbegin(), text.rend());
                if (totalRightHeight > 0)
                    totalRightHeight += gap;
                totalRightHeight += measureVerticalText(rotated, textScale);
            }

            const int maxRightOrigin = std::max(0, screenHeight - totalRightHeight);
            int       rightY         = std::clamp((screenHeight - totalRightHeight) / 2, 0, maxRightOrigin);
            if (rightY < reservedTop)
                rightY = std::min(std::max(reservedTop, 0), maxRightOrigin);

            int rightX = screenWidth - 20;

            for (size_t i = 0; i < rightTexts.size(); ++i) {
                std::string_view text = rightTexts[i];
                if (text.empty())
                    continue;
                std::string rotated(text.rbegin(), text.rend());
                rightY = screenHeight - measureVerticalText(rotated, textScale) - 8;
                drawTextRotated(framebuffer, rightX, rightY, rotated, true, textScale, true, 1);
                rightX -= 20;
            }

        } else {
            if (!activeRomName.empty())
                font16x8::drawText(framebuffer, 16, 16, activeRomName, 1, true, 1);

            const int fpsWidth = font16x8::measureText(fpsText, 1, 1);
            const int fpsX     = std::max(16, framebuffer.width() - fpsWidth - 16);
            font16x8::drawText(framebuffer, fpsX, 16, fpsText, 1, true, 1);

            int instructionY = framebuffer.height() - 24;
            font16x8::drawText(framebuffer, 16, instructionY, "START+SELECT BACK", 1, true, 1);

            instructionY -= font16x8::kGlyphHeight + 6;
            font16x8::drawText(framebuffer, 16, instructionY, scaleHint, 1, true, 1);

            if (!statusMessage.empty()) {
                const int statusWidth = font16x8::measureText(statusMessage, 1, 1);
                const int statusX     = std::max(12, (framebuffer.width() - statusWidth) - 12);
                const int statusY     = instructionY;
                font16x8::drawText(framebuffer, statusX, statusY, statusMessage, 1, true, 1);
            }
        }
        framebuffer.sendFrame();
    }

    void maybeSaveRam() {
        if (cartRam.empty() || activeRomSavePath.empty())
            return;

        FILE* file = std::fopen(activeRomSavePath.c_str(), "wb");
        if (!file) {
            setStatus("Save write failed");
            return;
        }
        const size_t written = std::fwrite(cartRam.data(), 1, cartRam.size(), file);
        std::fclose(file);
        if (written != cartRam.size()) {
            setStatus("Save short write");
        }
    }

    void loadSaveFile() {
        if (cartRam.empty() || activeRomSavePath.empty())
            return;

        FILE* file = std::fopen(activeRomSavePath.c_str(), "rb");
        if (!file)
            return;

        const size_t read = std::fread(cartRam.data(), 1, cartRam.size(), file);
        std::fclose(file);
        if (read != cartRam.size()) {
            // Ignore partial save files; keep data read so far.
            setStatus("Partial save loaded");
        }
    }

    void setStatus(std::string message) {
        statusMessage = std::move(message);
        browserDirty  = true;
    }

    [[nodiscard]] uint64_t nowMicros() const {
        if (highResClock)
            return highResClock->micros();
        const auto now = std::chrono::steady_clock::now();
        return static_cast<uint64_t>(
                std::chrono::duration_cast<std::chrono::microseconds>(now.time_since_epoch()).count());
    }

    void resetFpsStats() {
        fpsLastSampleMs = 0;
        fpsFrameCounter = 0;
        fpsCurrent      = 0;
    }

    static std::string buildSavePath(const RomEntry& rom, std::string_view romDir) {
        std::string slug = rom.saveSlug;
        if (slug.empty())
            slug = sanitizeSaveSlug(rom.name);
        if (slug.empty())
            slug = "rom";

        std::string result(romDir);
        if (!result.empty() && result.back() != '/')
            result.push_back('/');
        result.append(slug);
        result.append(".sav");
        return result;
    }

    static GameboyApp* fromGb(struct gb_s* gb) {
        if (!gb)
            return nullptr;
        return static_cast<GameboyApp*>(gb->direct.priv);
    }

    __attribute__((always_inline)) static bool shouldPixelBeOn(int value, int dstX, int dstY) {
        if (value >= 3)
            return true;
        if (value <= 0)
            return false;
        constexpr uint8_t pattern[2][2] = {{0, 2}, {3, 1}};
        const uint8_t     threshold     = pattern[dstY & 0x01][dstX & 0x01];
        return value > threshold;
    }

    static uint8_t romRead(struct gb_s* gb, const uint_fast32_t addr) {
        auto* self = fromGb(gb);
        if (!self)
            return 0xFF;
        // ScopedCallbackTimer timer(self, PerfTracker::CallbackKind::RomRead);
        if (!self->romDataView || addr >= self->romDataViewSize)
            return 0xFF;
        return self->romDataView[static_cast<std::size_t>(addr)];
    }

    static uint8_t cartRamRead(struct gb_s* gb, const uint_fast32_t addr) {
        auto* self = fromGb(gb);
        if (!self)
            return 0xFF;
        ScopedCallbackTimer timer(self, PerfTracker::CallbackKind::CartRamRead);
        if (addr >= self->cartRam.size())
            return 0xFF;
        return self->cartRam[static_cast<std::size_t>(addr)];
    }

    static void cartRamWrite(struct gb_s* gb, const uint_fast32_t addr, const uint8_t value) {
        auto* self = fromGb(gb);
        if (!self)
            return;
        ScopedCallbackTimer timer(self, PerfTracker::CallbackKind::CartRamWrite);
        if (addr >= self->cartRam.size())
            return;
        self->cartRam[static_cast<std::size_t>(addr)] = value;
    }

    static void errorCallback(struct gb_s* gb, const enum gb_error_e err, const uint16_t val) {
        auto* self = fromGb(gb);
        if (!self)
            return;
        ScopedCallbackTimer timer(self, PerfTracker::CallbackKind::Error);

        char buf[64];
        std::snprintf(buf, sizeof(buf), "EMU %s %04X", errorToString(err), val);
        self->setStatus(buf);
        self->unloadRom();
    }

    __attribute__((optimize("Ofast"))) static void lcdDrawLine(struct gb_s* gb, const uint8_t pixels[160],
                                                               const uint_fast8_t line) {
        auto* self = fromGb(gb);
        if (!self || line >= LCD_HEIGHT)
            return;

        ScopedCallbackTimer timer(self, PerfTracker::CallbackKind::LcdDraw);

        self->ensureRenderGeometry();
        const auto& geom = self->geometry;
        if (geom.scaledWidth <= 0 || geom.scaledHeight <= 0)
            return;

        const int yStart = geom.lineYStart[line];
        const int yEnd   = geom.lineYEnd[line];
        if (yStart >= yEnd)
            return;

        self->frameDirty = true;

        Framebuffer& fb = self->framebuffer;
        fb.frameReady();

        if (geom.scaledWidth == LCD_WIDTH && geom.scaledHeight == LCD_HEIGHT) {
            const int dstY     = yStart;
            const int dstXBase = geom.offsetX;
            for (int x = 0; x < LCD_WIDTH; ++x) {
                const bool on = shouldPixelBeOn(pixels[x], dstXBase + x, dstY);
                fb.drawPixel(dstXBase + x, dstY, on);
            }
            return;
        }

        const auto& colStart = geom.colXStart;
        const auto& colEnd   = geom.colXEnd;
        for (int x = 0; x < LCD_WIDTH; ++x) {
            const int drawStart = colStart[x];
            const int drawEnd   = colEnd[x];
            if (drawStart >= drawEnd)
                continue;
            for (int dstY = yStart; dstY < yEnd; ++dstY)
                for (int dstX = drawStart; dstX < drawEnd; ++dstX) {
                    const bool on = shouldPixelBeOn(pixels[x], dstX, dstY);
                    fb.drawPixel(dstX, dstY, on);
                }
        }
    }

    static const char* initErrorToString(enum gb_init_error_e err) {
        switch (err) {
            case GB_INIT_NO_ERROR:
                return "OK";
            case GB_INIT_CARTRIDGE_UNSUPPORTED:
                return "Unsupported cart";
            case GB_INIT_INVALID_CHECKSUM:
                return "Bad checksum";
            default:
                return "Init failed";
        }
    }

    static const char* errorToString(enum gb_error_e err) {
        switch (err) {
            case GB_UNKNOWN_ERROR:
                return "Unknown";
            case GB_INVALID_OPCODE:
                return "Bad opcode";
            case GB_INVALID_READ:
                return "Bad read";
            case GB_INVALID_WRITE:
                return "Bad write";
            case GB_HALT_FOREVER:
                return "Halt";
            default:
                return "Error";
        }
    }
};

class GameboyAppFactory final : public cardboy::sdk::IAppFactory {
public:
    const char*                         name() const override { return kGameboyAppName; }
    std::unique_ptr<cardboy::sdk::IApp> create(cardboy::sdk::AppContext& context) override {
        return std::make_unique<GameboyApp>(context);
    }
};

} // namespace

void setGameboyEmbeddedRoms(std::span<const EmbeddedRomDescriptor> descriptors) {
    gEmbeddedRomDescriptors = descriptors;
}

std::unique_ptr<cardboy::sdk::IAppFactory> createGameboyAppFactory() { return std::make_unique<GameboyAppFactory>(); }

} // namespace apps